Climate change can seem abstract. But if you live by the bay, it shouldn't. Within 40 to 60 years, coastal floods will affect as many as 90,000 residents in San Mateo County, the most vulnerable county in California. These people live on land less than 3 feet above the high tide line along San Francisco Bay, and rising sea levels resulting from global warming are likely to make previously unprecedented floods an annual event along the bay shore.

We say "these people" because many are alive today. People now under 40 years of age will see this happen in their lifetimes. More than $21 billion in property is also at risk, along with 220 sites listed by the U.S. Environmental Protection Agency as potential contamination threats, and schools, churches, community centers, police and fire stations, and more. Levees and flood control structures may protect around a quarter of these areas from floods at the 3-foot level, but only 10 percent of the area when floods are likely to crest 4 feet in the following decades.

In this visualization, one dot represents one real person. Climate change is not abstract.

Jon Christensen is a senior fellow in UCLA's cityLAB. Eric Rodenbeck is CEO and creative director of Stamen Design. This visualization is a collaboration among Climate Central, Stamen Design and New America Media. To follow this discussion on Twitter, use hashtags: #surgingseas and #1person1dot